CONICET | Buscador de Institutos y Recursos Humanos

Water deprivation is a physiological stress that triggers a different sequence of events to conserve body fluids and cardiovascular homeostasis. It is known that nitric oxide (NO) is involved in the cardiovascular adaptative response in several physiological and pathological conditions. However, the exact role played by NO in the pathogenesis of hypovolemic state induced by chronic dehydration remains to be defined. Therefore, this study was designed: 1) to evaluate the effect of chronic water deprivation on cardiovascular NO system in rats, and 2) to study the potential effect of a subsequent hydration on the alterations induced by this hypovolemic state. Male Sprague-Dowley rats (200g) were divided in: E1: water restriction during 3 days + 1 day of hydration (1 cycle), the cycle was repeated 8 times (32 days); C1: water ad libitum during 32 days; E2: 8 cycles of water restriction + water ad libitum during 1 month. We determined: body weight, systolic blood pressure (SBP) and hematocrit before and at the end of each experiment. At the end of experimental time the animals were sacrificed for evaluating NOS activity (14C L-arginina) in right atria (A), left ventricle (V) and thoracic aorta (Ao). Results: NOS Activity (pmol/g tissue. min) Groups Body weight (g) SBP (mmHg) Hematocrit (%) Au V Ao C1 285±10 108±2 48±1 352±18 283±17 326±14 E1 195±6*** 78±4*** 53±1** 277±17** 198±14** 356±12** E2 325±8# 102±3 49±2 319±15 249±19 306±16 The results are expressed as the mean ± SEM. *p< 0.05 vs C1, **p<0.01 vs C1, ***p<0.001 vs C1; #p<0.001 vs E1. Chronic water restriction decreased body weight (32%) and plasmatic volume (18%) associated with a reduction in SBP and NOS activity in the cardiovascular system. These parameters recovered basal values after one month of oral hydration. According to our results, we suggest that cardiovascular NO system activity depends on individual hydration state.